Pros
As other folks have mentioned, it's a good resume builder, particularly if you are a CPA. I worked for Deloitte for 8 years in various professional services management roles within management/strategy consulting, technology and financial advisory services. The staff you'll work with are absolutely great. Smart, mostly good-natured, team-oriented.
Cons
Wow, where to begin. There are so many. As someone else suggested, if you can go in with a firm plan to only remain there 2 years, then definitely do it. Lifestyle is pretty poor. You will work many hours to be viewed as a 'team player'. They WILL pay you well for it. And chances are 2 years will slip by and you'll still be there, cursing yourself for your love of the money. The marketing department is a world onto itself. It seems to spend all day generating glossy e-brochures we'd get telling us how great work/life balance is (maybe it is for them, but not for the rest of us). The partners don't read or follow this stuff. Utilization is king. If you aren't busy on a billable engagement, no one cares what you bring to the table. Seriously, it is irrelevant. Partners are solely about profit. To the point when times get tough, they immediately move to layoff their talent. Keep in mind, this is professional services, so they're laying off the folks they'll need when the goodtimes return. I wish I had left this firm after 2-3 years. I made good money, got the promotions, yadda yadda. But there is a limited return on your level of effort. The consulting work is definitely 'generalist' and constantly changing. You don't get some amazing skillset that makes you irreplaceble. And the partnership overhypes their staff talent to clients to justify an average billing rate in the $500's. I mean, would you pay $20K a week for some college kid or MBA who didn't know your industry and the particular problem at hand thoroughly? Of course not. And so, you are stuck in the middle between unreasonable (but understandable) client expectations and a partnership which just wants it done well enough to collect receipts.